init.rc文件里面启动c++程序，通过jni调用java实现

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</pre><p>注：如果是自己的myself.jar包，还要改动如下：</p><p>target/product/core_base.mk PRODUCT_BOOT_JARS := core:myself</p><p></p><p>功能：手机开机后要写个标志位。已有实现，就是收到开机广播后，启动服务读取bp中的标志位（java代码需要等待ril准备好），并把这个标志位写入到ap中（java代码调用c++）。后来遇到的问题：实际应用中发现，接收开机广播等待的时间更长，需要提前写入ap时间。解决方案：在init.rc文件里面启动c++程序，通过jni调用java实现。精简代码如下：C++程序代码:</p><p></p><pre code_snippet_id="517675" snippet_file_name="blog_20141113_2_8082170" name="code" class="plain">#define LOG_TAG "testmain"#define LOG_NDEBUG 0#include <dlfcn.h>#include <cutils/log.h>#include <utils/Log.h>#include <jni.h>using namespace android;void wirtePsCaliValToKernel();int main (int argc, char * argv[]){    ALOGI("start c");    wirtePsCaliValToKernel();    ALOGI("start c end");    return 0;}void wirtePsCaliValToKernel() {    JavaVM* vm;    JNIEnv* env;    // start a VM    JavaVMInitArgs args;    JavaVMOption opt;    opt.optionString =        "-agentlib:jdwp=transport=dt_android_adb,suspend=n,server=y";    args.version = JNI_VERSION_1_4;    args.options = &opt;    args.nOptions = 1;    args.ignoreUnrecognized = JNI_FALSE;    void* libdvm_dso = dlopen("libdvm.so", RTLD_NOW);    ALOGE_IF(!libdvm_dso, "DdmConnection: %s", dlerror());    void* libandroid_runtime_dso = dlopen("libandroid_runtime.so", RTLD_NOW);    ALOGE_IF(!libandroid_runtime_dso, "DdmConnection: %s", dlerror());    if (!libdvm_dso || !libandroid_runtime_dso) {        goto error;    }    jint (*JNI_CreateJavaVM)(JavaVM** p_vm, JNIEnv** p_env, void* vm_args);    JNI_CreateJavaVM = (typeof JNI_CreateJavaVM)dlsym(libdvm_dso, "JNI_CreateJavaVM");    ALOGE_IF(!JNI_CreateJavaVM, "DdmConnection: %s", dlerror());    jint (*registerNatives)(JNIEnv* env, jclass clazz);    registerNatives = (typeof registerNatives)dlsym(libandroid_runtime_dso,        "Java_com_android_internal_util_WithFramework_registerNatives");    ALOGE_IF(!registerNatives, "DdmConnection: %s", dlerror());    if (!JNI_CreateJavaVM || !registerNatives) {        goto error;    }    if (JNI_CreateJavaVM(&vm, &env, &args) == 0) {        jclass startClass;        jmethodID readPsMeth;        // register native code        if (registerNatives(env, 0) == 0) {            startClass = env->FindClass("android/hardware/Camera");            if (startClass) {                ALOGI(" startclass is ok");                //readPsMeth = env->GetStaticMethodID(startClass, "getCurrentFocusPosition", "(I)V");                readPsMeth = env->GetMethodID(startClass, "getCurrentFocusPosition", "()I");                int result = -1;                if (readPsMeth) {                    ALOGI("readPsMeth is ok, result = %d ",  result);                    result = env->CallStaticIntMethod(startClass, readPsMeth);                    ALOGI("readPsMeth is ok end, result = %d ",  result);                }else{                    ALOGE("-->> readPsMeth is fail");                }            }else{                ALOGE("startclass is fail");            }        }    }    return;error:    if (libandroid_runtime_dso) {        dlclose(libandroid_runtime_dso);    }    if (libdvm_dso) {        dlclose(libdvm_dso);    }}

Android.mk:

LOCAL_PATH:= $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE:= testmainLOCAL_SRC_FILES:=     \    testmain.cppLOCAL_C_INCLUDES :=LOCAL_MODULE_TAGS := optional engLOCAL_SHARED_LIBRARIES += libcutils   \                          libutils    \                          liblog    \                          libandroid_runtime \                          libnativehelper \                          libdl \include $(BUILD_EXECUTABLE)

init.rc修改:

class 值为main时才能开机自动启动

service testmain /system/bin/testmainclass mainuser rootoneshot

end

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